Answered by Shaykh Faraz Rabbani
If I literally bite my brother on his back, would that be considered backbiting? Would I have to restart my muraqaba dars?
Walaikum assalam wa rahmatullah,
If he enjoys it, it is fine in private, but unmanly in public.
If with desire, haram.
If he does not like it, then it is disliked.
If it causes pain, it would be prohibitively disliked.
If it causes serious harm, it would be haram.
In none of the cases would it be considered backbiting, unless it uncovers something about your brother that he does not like uncovered (such as a phobia or physical/emotional weakness).
And Allah knows best.
Wassalam,
Faraz Rabbani